From Wikipedia, the free encyclopedia. Kate O'Mara (born 10 August 1939, in Leicester) is an English film, stage and television actress. She is perhaps best known for her role as Caress Morell, Alexis Carrington's sister in Dynasty. She also played the villain, The Rani in Doctor Who. Description above from the Wikipedia article Kate O'Mara, licensed under CC-BY-SA, full list of contributors on Wikipedia.